I have a 3 storey house built in 2000. My bathroom is on the 3rd floor and I noticed mushrooms growing out of the skirting alongside the toilet. We have lifted the lino, removed the skirting and the tiled frame enclosing the pipework.There was a lot more ground damp, black soot on the walls and more mushrooms. Much wetter below the bend on the overflow pipe which we have tightened. Do we need to do more?